Solar controller for battery charging?

[N8N]

Good morning

For a while now I've had a Harbor Freight solar panel and charge controller in one of my seldom used cars that has a high key off current draw. I think the charge controller has packed it in however. I don't like it anyway as it doesn't have any kind of readout, just LEDs to indicate charging and high/low voltage. Anyway I went to move it to another car yesterday and the "charge" light wasn't lit. Couldn't find a multimeter quickly but will check it out more thoroughly.

In any case I need another one of these setups so I'm going to need another charge controller anyway. Does anyone have a recommendation for a good charge controller that would work for my use? I'm basically using a small (10-20W) solar panel to act as a battery tender for a car that can't be parked by a receptacle. Thanks!

 

[sbslider]

A tricky thing with most charge controllers is that they are rated at currents that are an order of magnitude higher than you will be using. Your small panel probably puts out at most 1A, and all charge controllers that I have found are rated for 10A or more. The one I used to have would never transition from charging to float, and it eventually fried my batteries. I have another 10A one made by Newpowa that I used for charging lithium bank. It works great for this. I've considered using a second one for charging my camper battery, but I DVMs say its displayed voltage is a couple tenths of a volt higher than what my meter reads. Since my meter isn't calibrated, I'm not certain which is off. I plan to get a new meter soon, but until then I can say maybe this would work for you, but check it out with your DVM. The one I got is the 10A PWM version: https://www.amazon.com/Newpowa-10A-...XQ1P/ref=cm_cr_arp_d_pl_foot_top?ie=UTF8&th=1

 

[N8N]

cool. so when you say lithium bank I assume this is either 3x or 6x 3.7V cells? and you're happy with it? That looks just like what I want, as long as it works - cheap, will float a 12V lead-acid battery, and just has some kind of display that I can periodically check and make sure it's working.

I actually drove the car this was on for the first time in a while today and it didn't seem like the battery was topped up, now granted it would have been dead without the solar panel on it but it didn't feel like it was charged to capacity. But as I say I only have three LEDs now so I don't have a picture of what's going on.

 

[orbital]

+

I use HQST solar controllers (MPPT unit connected to my solar setup )
Really recommend them

This PWM* unit would work fine as a trickle charger. Remember to connect to the battery first, then to panel.
$21 using coupon code 4HQST

30A 12V/24V PWM Flush Mount Solar Charge Controller - Negative Ground

OVERVIEW For those committed to off-grid living, this HQST 30 Amp Flush Mount Solar Charge Controller allows you to keep your battery powered via solar panels wherever you happen to be - traveling by RV or truck or maintaining a convenient and reliable solar-powered solution for your cabin or...

hqsolarpower.com

you'd think it's a matter of time, some manufactures will have a small solar panel in the window trickle charging the battery.
that would make sense to me

*30A is the max it can do,, it obviously doesn't do that all the time or for the size panel you have.
Seems like you panel does 1~2A and that's fine.

 

[sbslider]

cool. so when you say lithium bank I assume this is either 3x or 6x 3.7V cells? and you're happy with it? That looks just like what I want, as long as it works - cheap, will float a 12V lead-acid battery, and just has some kind of display that I can periodically check and make sure it's working.

I actually drove the car this was on for the first time in a while today and it didn't seem like the battery was topped up, now granted it would have been dead without the solar panel on it but it didn't feel like it was charged to capacity. But as I say I only have three LEDs now so I don't have a picture of what's going on.

Yeah, I got an old e-bike battery someone was giving away. It has 13s 4p cells. I found one of the 13 "rows" was bad, so I cut that out, and rewired it as 3s-16p. so I have my controller programmed to shut off at 11.9V, which gives me more like 12.0V on the battery. I also have a cell balancer connected to keep the stacks from getting over charged. It's been like this for a year and a half and works well.

Another option would be to use the controller in lithium mode and just cap the max charge voltage to X, and let it sit there. Your battery won't be fully charged, but it would be pretty close and likely just fine.

Perhaps orbital's recommendation is better, I only know what I've used.

 

[N8N]

Well I ordered the Amazon one but I apparently need two; I got home and it was sunny out and the panel was putting out 15.something volts but the charge controller was not charging. Verified all connections to battery and panel and still no bueno. Got the battery in landlady's car on a recond cycle on my CTEK 7000, but now I apparently need solar in both that car and my BMW. Fortunately the battery in the BMW had enough charge to start it yesterday, it's 6 years old so already on borrowed time.

Amazon controller will be here tomorrow, and I picked up another solar panel at HF on the way home from work.

 

[N8N]

Just ordered the other one recommended.